I have a 94 F-150 with a straight 6 cylinder engine and an automatic transmission that has around 200k miles on it. For a couple of years now it has had a random problem with being slow to shift into drive sometimes. It will always shift into reverse right away but sometimes it can take a minute or two to shift into drive. It usually shifts into drive faster after it has been driven for a little while but not always. It seems to help when I put it in reverse first and then shift into drive but that might just be because that uses up some of the wait time. I have not noticed any other shifting problems while driving after it goes into gear. Has anyone else run into this problem before or does anyone have any suggestions about what is wrong? I don't have much mechanical experience but I am having fun learning a lot of stuff while working on my truck.

Yes the fluid level is fine. I changed the transmission fluid shortly after I bought the truck about 4 years ago. I talked to a local transmission guy a few months ago and he said start by changing the fluid but my mechanic said that if the fluid was the problem it would be slow to shift into reverse also.

Thanks for the ideas and info. I have had the same thought about it being a reminder to not be in a hurry. I am always a little concerned about if today is the day it will decide not to shift at all but so far it hasn't let me down yet.

I would change the filter and fluid.
Do the torque converter at the same time.
Ford recommends type 5 now.

I had this problem before my 2015 issues began (transmission blew, then we put a new engine in after that, now I'm $7K into rebuilding this whole truck and still struggling with a fuel/electrical issue).

Anyway, the flex plate in the torque converter was perfectly cracked in a circle around its attachment holes (engagement). It shouldn't have spun, but the cracks fit the outer part of the cracked flex plate and would catch, allowing me to engage the transmission with a completely broken torque converter. It was something to see when we pulled it out.

We pulled it out AFTER the mechanic put a new replacement AOD transmission. He didn't catch the flex plate. Found during the engine swap 3-4 weeks later. Not a good mechanic.

It caused symptoms similar to what you're describing.

Also, if you're E40D, grounds to the wiring harness should be checked. Intermittent ground could cause the situation to have slow shifting or rough shifting. I'm currently in that situation now, but because of a ground between the relays and the fuel pumps. Not the same thing as what you're chasing, but worth looking at that wiring harness on the transmission. Unsure if an AOD transmission has the same wiring to check. I had an AOD replacement in 2015 by the bad mechanic and my electrical was eliminated until I got an E40D back in 2 years later and could reconnect the tranny to the wiring harness.